▎ 摘　　要

We fabricated reduced graphene oxide (rGO)-reinforced Al2O3 composites by spark plasma sintering and studied the effect of graphene oxide (GO) dimensions on the microstructure and mechanical properties of composites. The thin GO led to both grain size refinement and grain boundary pinning effects. The Al2O3 composite reinforced by thin and large GO had higher hardness than that reinforced by thick and small GO. The addition of thick GO leads to a reduction of hardness and generation of lateral cracks at the Al2O3 grain boundaries under indentation due to low rGO interlayer strength. The rGO distribution in the Al2O3 matrix was studied. A model calculation showed that the spacing between two parallel rGO platelets was one Al2O3 grain at rGO addition of 0.77 wt%. We concluded that the increased hardness of rGO/Al2O3 composites is due to the fine grain size and thin rGO at Al2O3 grain boundaries.